JP2005351888A - Determination method of iron and steel slug and method for predicting its solidified state - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for determining iron and steel slug to be used according to operating environments and purposes when iron and steel slug is used as a sand covering material or a back-filling material. <P>SOLUTION: An arranging location of a sand covering material or a back-filling material is determined (S101). Iron and steel slug to be used is temporarily determined (S102). In the case that the sand covering material or the back-filling material made of temporarily determined iron and steel slug is arranged at the arranging location, the state of solidification is predicted on the basis of at least either the concentration of hydroxyl group ions or the concentration of calcium ions in pore water of the iron and steel slug at the arranging location (S103) to determine whether the predicted state of solidification is in a desired state or not (S104). In the case that it is not in the desired state (No in S105), the evaluation of the temporarily determined iron and steel slug is repeated until the desired state of solidification is achieved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for determining a steel slag to be used when the steel slag is used as a sand covering material or a backing material. More specifically, according to the present invention, when using steel slag as a sand covering material or a backing material, the solidification strength of the steel slag to be disposed is an appropriate value, depending on the use environment and purpose of use. The present invention relates to a method for determining steel slag to be used.

  In order to improve the bottom quality and water quality of the water area, a technique for supplying sand covering material to the bottom mud is known. Conventionally, natural stone and mountain sand have been used. However, as the awareness of the global environment increases, steel slag generated in the steel manufacturing process has attracted attention as an alternative material.

  When steel slag is used as sand-capping material, it is possible to take advantage of the characteristics of slag and respond to various purposes. For example, when it is desired to securely contain seabed pollutants, it is possible to suppress elution and diffusion of harmful substances by consolidating slag on the seabed using the latent hydraulic properties of slag. When it is desired to enrich marine resources on the seabed, it is possible to increase biological productivity by eluting minerals contained in slag.

Various techniques have been proposed for the use of steel slag as sand-capping material. For example, in Patent Document 1, when converter slag having a particle size of about 1 mm is used as a sand-capping material, hydrogen sulfide and phosphorus components may be removed by CaO and Fe ₂ O ₃ components in converter slag. It has been reported. Patent Document 2 proposes a technique that uses both steelmaking slag and blast furnace granulated slag as sand-capping material. Specifically, a lower layer made of sand-covering material containing steelmaking slag is formed on the bottom mud, and an upper layer made of sand-covering material containing blast furnace granulated slag is formed on the lower layer.

  It is preferable that the state of consolidation of the steel slag supplied to the water area is controlled according to the purpose. As described above, when slag is used for containment of seabed pollutants, it is preferable that the slag disposed on the seabed be consolidated. On the other hand, when it is desired to expand marine resources on the seabed, it is preferable that the slag disposed on the seabed is not consolidated. However, so far, no sufficient study has been made on factors affecting the consolidated state of steel slag. In particular, when steel slag is placed in the sea, various factors such as tidal speed, movement of pore water existing between the slags, and the thickness of the sand covering material affect the consolidation of the slag. Therefore, it was difficult to predict the consolidated state.

The use of steel slag can be considered as a quay lining material, but as in the case of sand-capping materials, sufficient control of the steel slag consolidation has not been studied.
JP-A-3-4988 JP 2001-256293 A

  As described above, when steel slag is used as a sand-capping material or a backing material, it is difficult to predict the consolidation of slag, and in some cases, there is a possibility that inappropriate steel slag may be used. is there. For example, when steel slag is supplied as a sand covering material in order to contain sea bottom pollutants, there is a risk that the sea bottom pollutants may elute and diffuse without solidification of the steel slag.

  Therefore, an object of the present invention is to provide a means for determining steel slag to be used according to the use environment and purpose when using steel slag as a sand-capping material or a backing material.

The present invention
(1) A method for determining a steel slag used as a sand-capping material or a backing material, the step (a) of determining the location of the sand-covering material or the backing material, and a temporary determination of the steel slag to be used The step (b) and the caking condition when the sand-covering material or backing material composed of the temporarily determined steel slag is arranged at the arrangement location, the hydroxyl group ion concentration in the steel slag pore water at the arrangement location or A steel slag comprising a step (c) of predicting based on at least one of calcium ion concentrations and a step (d) of determining whether or not the predicted consolidated state is a desired state. How to determine,
(2) Steps (b), (c), and (d) are performed on steel slag different from the already determined steel slag when it is determined that the predicted consolidated state is not a desired state. The method for determining steel slag as described in (1), characterized in that it is repeated until it is determined that the predicted consolidated state is a desired state.
(3) The step (c) is based on at least one of the time integral value of the hydroxyl ion concentration calculated based on the following formula 1 or the time integral value of the calcium ion concentration calculated based on the following formula 2. The method for determining steel slag as set forth in (1) or (2), characterized in that it is a stage for predicting the consolidated state,

(In the formula, [OH ⁻ ] represents the hydroxyl group ion concentration in the pore water at the arrangement location, and t represents time)

(In the formula, [Ca ²⁺ ] represents the calcium ion concentration in the pore water at the arrangement location, and t represents time)
(4) The concentration of the hydroxyl ion in the formula 1 and the concentration of the calcium ion in the formula 2 are calculated based on an advection / diffusion equation represented by the following formula 3, Determination method of steel slag as described,

(In the formula, C is the concentration of hydroxyl ion or calcium ion (mol / L), t is time (s), D is a diffusion coefficient, and h is from the upper surface of the sand-capping material or backing material. Is the reaction rate coefficient (1 / s) indicating the ease of elution of hydroxyl ions or calcium ions from the slag, and ν is the pore water velocity (cm / s). is there),
(5) The reaction rate coefficient λ is calculated by measuring an ion elution rate α (mol / L · s) indicating ion elution from steel slag in a reference solution. 4) Method for determining steel slag as described in
(6) A method for predicting solidification status of steel slag used as sand-capping material or backing material, where the sand-covering material or backing material is placed, the steel slag used, and the steel slag gap Based on at least one of hydroxyl ion concentration or calcium ion concentration in water, it is characterized by predicting the consolidated state in the case where the sand covering material or backing material made of the steel slag is disposed at the placement location, Method for predicting solidification status of steel slag,
(7) The consolidation state is predicted based on at least one of the time integral value of the hydroxyl ion concentration calculated based on the following formula 1 or the time integral value of the calcium ion concentration calculated based on the following formula 2. The solidification state prediction method of steel slag according to claim 6,

(In the formula, [OH ⁻ ] represents the hydroxyl group ion concentration in the pore water at the arrangement location, and t represents time)

(In the formula, [Ca ²⁺ ] represents the calcium ion concentration in the pore water at the arrangement location, and t represents time)
(8) The concentration of the hydroxyl ion in the formula 1 and the concentration of the calcium ion in the formula 2 are calculated based on an advection / diffusion equation represented by the following formula 3, Solidification status prediction method of steel slag as described,

(In the formula, C is the concentration of hydroxyl ion or calcium ion (mol / L), t is time (s), D is a diffusion coefficient, and h is from the upper surface of the sand-capping material or backing material. Is the reaction rate coefficient (1 / s) indicating the ease of elution of hydroxyl ions or calcium ions from the slag, and ν is the pore water velocity (cm / s). is there),
(9) The reaction rate coefficient λ is calculated by measuring an ion elution rate α (mol / L · s) indicating ion elution from steel slag in a reference solution. 8) Method for predicting solidification status of steel slag as described in 8),
It is.

  By using this invention, it is possible to determine the steel slag which should be used according to a use environment and the objective. By using an appropriate steel slag, the steel slag can be used more effectively as a sand-capping material or a backing material. For example, if you want to consolidate steel slag placed on the seabed as a sand-capping material in order to prevent the elution and diffusion of seabed pollutants, select steel slag that is easy to consolidate in the environment in which it is used. Elution and diffusion of pollutants can be effectively prevented.

  1st of this invention is the determination method of the steel slag used as sand-capping material or a backing material, Comprising: The stage (a) which determines the arrangement | positioning location of a sand-covering material or a backing material, and the steel used The step (b) of tentatively determining the slag and the consolidated state when the sand-capping material or backing material made of the temporarily determined steel slag is arranged at the arrangement location are shown in the steel slag pore water at the arrangement location. A step (c) of predicting based on at least one of a hydroxyl ion concentration or a calcium ion concentration, and a step (d) of determining whether or not the predicted consolidated state is a desired state. This is a method for determining steel slag.

  One of the points of the present invention is to use chemical factors such as hydroxyl group ion concentration and calcium ion concentration in predicting the future consolidated state. First, this will be described.

  As factors affecting the consolidation phenomenon of steel slag, there may be physical factors such as particle size and compaction density. However, it is difficult to grasp the entire consolidation phenomenon even though the effects on these consolidation phenomena can be clarified. Therefore, the present inventors investigated the correlation between caking and chemical factors such as ion concentration and pH in pore water. In addition, in this application, pore water means the water which exists between the steel slag particle | grains arrange | positioned as a sand covering material or a backing material. The calcium ion concentration in pore water in steel slag is measured by collecting pore water from an actual slag layer and measuring the concentration in a laboratory or the like. More specifically, for example, the calcium ion concentration can be measured according to JIS K0102. The hydroxyl ion concentration can be measured by installing a pH meter in the actual slag layer.

The following mechanisms can be considered as the mechanism of elution of ions from steel slag and the formation of consolidated substances on the surface of steel slag. First, Ca ²⁺ , SiO ₄ ⁴⁻ , Al (OH) ₄ ⁻ , OH ^{− and the} like are eluted from the steel slag. By elution of the hydroxyl ions, the pH around the steel slag increases.

By increasing the concentration of various ions eluted and reaching a certain saturation condition, a solidified substance (hydrate) is generated on the surface of the steel slag. For example, a solidified substance represented by the general formula αCaO · βSiO ₂ · γH ₂ O is generated by reaction with calcium ions, silicate ions, and hydroxyl ions (aCa ²⁺ + bH ₃ SiO ⁴ + + cOH ⁻ → αCaO · βSiO ₂ · γH ₂ O). The consolidated substance deposited on the surface of the steel slag acts as a binder, and the steel slags are bound together to form an aggregate made of steel slag hardened with high strength.

In the above mechanism, it is considered that the production rate V of the consolidated substance CSH (αCaO · βSiO ₂ · γH ₂ O) is calculated by the following formula 4. In Equation 4, k ₁ is a reaction rate constant.

In order to evaluate the consolidation speed V, the present inventors investigated the relationship between the ion elution amount from steel slag and pH. FIG. 1 is a graph showing the relationship between pH of each ion of Ca ²⁺ , SiO ⁴⁻ , and Al (OH) ₄ ⁻ . In FIG. 1A, the vertical axis represents the amount of Ca ²⁺ eluted, in FIG. 1B, the vertical axis represents the amount of SiO ⁴ -eluted, and in FIG. 1C, the vertical axis represents the amount of Al (OH) ₄ ⁻ eluted. It is. As shown in FIG. 1A, the amount of calcium ions eluted increases with increasing pH. That is, when the elution amount of hydroxyl ions increases, the elution amount of calcium ions also tends to increase. From FIG. 1B, it can be seen that the elution amount of SiO ⁴⁻ ions is constant regardless of pH. As shown in FIG. 1C, the elution amount of Al (OH) ₄ ⁻ tends to increase with an increase in pH as in the case of calcium ions.

When there is a correlation between the calcium concentration and the hydroxyl ion concentration, and the H ₃ SiO ⁴⁻ ion concentration is a constant value, the equation 4 can be modified as shown in the following equation 5. That is, the consolidation rate V of the consolidated material on the steel slag surface can be regarded as a reaction that depends only on the hydroxyl ion concentration.

  Since the hydroxyl ion concentration and the calcium ion concentration have the relationship shown in FIG. 1A, the consolidation rate V can be regarded as a reaction that depends only on the calcium ion concentration. In addition, since the consolidation speed V depends on the hydroxyl ion concentration, the consolidation speed V naturally depends on pH and pOH. In addition, when implementing the method of this invention using pH or pOH, it is equivalent to evaluating the consolidation condition using a hydroxyl group ion concentration in fact. Therefore, the embodiment for evaluating the consolidation state using pH or pOH is included in the technical scope of the invention for evaluating the consolidation state using the hydroxyl ion concentration.

  If the assumption shown in Equation 5 is correct, the amount of solidified material produced depends on the amount of hydroxyl ions produced, and as the cumulative amount of hydroxyl ions produced increases, the amount of solidified material produced increases. The strength of should be higher. Based on this assumption, the causal relationship between the elution amount of hydroxyl ions from steel slag and the consolidation strength was investigated. FIG. 2 is a graph showing the relationship between the elution amount of hydroxyl ions and the consolidation strength when ε = 1 is assumed in Equation 5. In FIG. 2, the horizontal axis represents the cumulative integrated value of the hydroxyl group ion concentration, and the vertical axis represents the uniaxial compressive strength of the steel slag. As shown in the figure, the uniaxial compressive strength of the steel slag was higher as the cumulative amount of hydroxyl ion concentration was increased. This result is considered to support the above assumption. In addition, although the said description is made about hydroxyl ion, it is thought that the same relationship is materialized also about calcium ion. In the following description, for the sake of convenience, hydroxyl ions (pH) will be mainly described, but it is not intended to exclude a method for predicting the consolidation state using calcium ions.

  As described above, the consolidation strength is proportional to the cumulative amount of hydroxyl ion concentration. If this knowledge is utilized, it is possible to predict the consolidated state of sand-capping material or backing material. For example, consider a case where a predetermined steel slag is placed on the seabed as a sand covering material. First, the thickness of the sand covering material arranged on the seabed is determined. Next, when a predetermined steel slag is placed on the seabed as a sand-capping material, what kind of pH distribution (hydroxyl ion concentration distribution) occurs in the steel slag placed as the sand-capping material is investigated. . The pH distribution may be determined based on an advection / diffusion equation as described later, or a laboratory model may be actually created and evaluated. In general, in the sand cover, the pH in the vicinity of the contact surface with the seawater is low, the pH increases as it advances in the depth direction of the sand cover, and there is a tendency that the pH does not fluctuate beyond a certain depth. Therefore, the deeper the sand cover, the higher the consolidation speed V, and the steel slag tends to solidify quickly.

  However, the pH distribution in the sand cover arranged on the seabed varies depending on the steel slag used. For this reason, even when the sand-capping material is placed on the same seabed for one year, certain steel slag progresses to the vicinity of the sand-covering surface, and certain steel slag progresses to a depth of 30 cm, Some steel slag does not progress at all. By using the method of the present invention, it is possible to infer how the consolidated state will be after a predetermined period of time, so select and use the appropriate steel slag according to the usage environment and purpose Is possible. For example, when steel slag is supplied as a sand-capping material to contain seabed pollutants, steel slag that tends to have a high pH inside the sand-capped sand is used as the sand-clad material so that consolidation can proceed quickly. That's fine.

  Hereinafter, the steel slag determination method of this invention is demonstrated in detail in order of a process using FIG. FIG. 3 is a flowchart illustrating a method for determining steel slag according to the present invention.

  First, the arrangement | positioning location of a sand covering material or a backing material is determined (S101). The pH distribution inside the sand-covering material or the inside of the backing material is affected by the location of the sand-covering material or the backing material. For example, the pH distribution is affected by the usage environment peculiar to the location such as the ocean current speed, tide level fluctuation, and water depth. In order to calculate an accurate pH distribution inside the sand covering material or the inside of the backing material, it is preferable to consider more factors. However, as the factors to be considered increase, it becomes difficult to calculate the pH distribution. In addition, when the pH distribution is measured using a laboratory-level model, the cost required for model production increases. For this reason, when it is desired to obtain the maximum result at a low cost, the pH distribution may be calculated without considering these factors, which are assumed not to have a large effect on the pH distribution. The pH distribution may be calculated by regarding it as a constant value.

  Next, the steel slag to be used is provisionally determined (S102). Although the future consolidation status varies depending on the steel slag used as sand-capping material or backing material, the steel slag to be used is temporarily determined at this stage. When using a laboratory-level model to predict the consolidated state of sand-capping material or backing material, it is advisable to prepare steel slag that is substantially the same quality as the steel slag that is actually planned to be used.

  The type of slag that is provisionally determined is not particularly limited. As steel slag, blast furnace slag and steelmaking slag may be used. Examples of the blast furnace slag include blast furnace slow-cooled slag and blast furnace granulated slag. Examples of steelmaking slag include converter slag, pretreatment slag, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, electric furnace reduction slag, electric furnace oxidation slag, secondary refining slag, and ingot slag. . Two or more of these may be used as steel slag.

  In some cases, materials other than steel slag may be contained in the sand-capping material or the backing material made of steel slag. Examples of materials other than steel slag include coal ash such as fly ash and bottom ash, crushed waste concrete, waste brick, and waste refractory, municipal waste slag, dredged sand, and dredged soil. Two or more of these may be used in combination, or materials other than these may be used. When mixing steel slag with other components, the mixing ratio of the steel slag is such that some effects due to steel slag such as mineral elution from slag, hydrogen sulfide fixation, and phosphorus fixation are secured to some extent. The content is preferably 50% by mass or more.

  After temporarily determining the steel slag, the caking condition when the sand-covering material or backing material made of the temporarily determined steel slag is arranged at the arrangement location is determined by at least one of the hydroxyl ion concentration or the calcium ion concentration at the arrangement location. (S103).

  As described above, the consolidation state can be predicted based on the cumulative value of the hydroxyl group ion concentration. The higher the hydroxyl group ion concentration at the predetermined location, the higher the consolidation speed V and the rapid consolidation of the steel slag. The consolidation state after the elapse of a predetermined period is predicted based on the time integrated value of the hydroxyl group ion concentration in the steel slag pore water at the arrangement location, calculated by the following formula 1.

In the formula, [OH ⁻ ] represents the hydroxyl group ion concentration in the pore water at the arrangement location, and t represents time. For example, when it is desired to predict the consolidated state after one year, the cumulative concentration of hydroxyl ions for one year is calculated. It is also possible to predict the consolidation state based on the time integral value of the calcium ion concentration. In this case, the time of the calcium ion concentration in the steel slag pore water at the arrangement location calculated by the following equation 2 Predicted based on analysis values.

In the formula, [Ca ²⁺ ] represents the calcium ion concentration in the pore water at the arrangement location, and t represents time.

  When the time integrated value of the hydroxyl ion concentration is calculated, the consolidation state is predicted based on the time integrated value of the hydroxyl ion concentration. In the prediction of the consolidation state, it is preferable to investigate the relationship between the time integral value of the hydroxyl ion concentration and the consolidation strength in the sand-capping material or the backing material to be used, and predict based on the relationship. For example, the relationship between the cumulative value of the hydroxyl ion concentration and the uniaxial compressive strength shown in FIG. And the uniaxial compressive strength when the period passes is estimated from the time integral value of the hydroxyl group ion concentration until a predetermined period.

  The distribution of the ion concentration in the sand-capping material or the backing material varies depending on the location of the sand-covering material or the backing material and also the position of the sand-covering material or the backing material. FIG. 4 shows the pH distribution in the sand cover when only the blast furnace granulated slag is disposed as the sand covering material, and the pH in the sand cover when the mixture of the ground granulated blast furnace slag and the steelmaking slag is disposed as the sand covering material. It is a graph which shows distribution. As shown in FIG. 4, generally in the sand covered sand, the pH at the part in contact with the seawater is generally the lowest, and the pH gradually increases as the sand covers the depth direction. When a certain depth is reached, the increase in pH stops and the pH reaches a certain value. As described above, since a constant pH distribution can occur in the sand-capped sand, it is preferable to calculate the ion concentration distribution at the arrangement location in order to accurately predict the consolidation state at the arrangement location.

  In the calculation of the ion distribution at the arrangement location, the advection / diffusion equation represented by the following Equation 3 can be applied.

  In the formula, C is a concentration of hydroxyl ion or calcium ion (mol / L), t is time (s), D is a diffusion coefficient, and h is from the upper surface of the sand-capping material or backing material. Depth (cm), λ is a reaction rate coefficient (1 / s) indicating easiness of elution of hydroxyl ions or calcium ions from slag, and ν is a rate of pore water (cm / s) .

  The diffusion coefficient D is determined by separately performing a test for measuring a change in ion concentration in the slag layer to which an ion concentration difference is given. The diffusion coefficient D can be measured by the following method, for example. First, steel slag and high ion concentration water are supplied in the same layer. The steel slag and the high ion concentration water are partitioned so as not to be mixed. A measuring device such as a pH meter is installed in the steel slag at every predetermined distance from the partition. The partition is removed, the ion concentration change over time from the time when the partition is removed is measured, and the diffusion coefficient D is calculated from the ion concentration change over time.

  The reaction rate coefficient λ is calculated by measuring the ion elution rate indicating the ion elution from the steel slag in the reference solution. For example, the reaction rate coefficient λ is calculated from the amount of time variation of calcium ion concentration or pH in a solution in which steel slag is immersed.

  The velocity ν of pore water can be calculated using commercially available analysis software from conditions such as tidal currents and surrounding head differences (potential). Examples of commercially available analysis software include “Visual MODFLOW Pro Japanese version for Windows” (manufactured by Waterloo Hydrologic).

  In the above, in the case of calcium ions, the calcium ion concentration (mg / L) and the reaction rate coefficient λ (1 / s) representing the ease of elution of calcium ions from the slag can be used.

  Based on the calculation of the hydroxyl ion concentration distribution at the arrangement location, the time integral value of the hydroxyl ion concentration, and the relationship between the time integral value of the hydroxyl ion concentration and the consolidation strength, the consolidation state when a predetermined time elapses is predicted. As an example, FIG. 4 shows the pH distribution in the sand covering when various steel slags are used as the sand covering material. In the figure, the pH closer to the sea surface is lower, and the pH is higher as the depth h increases. From this pH distribution, the distribution of the uniaxial compressive strength in the depth direction at an arbitrary elapsed time can be obtained by using the expression 1 and, if necessary, the expression 3 and the relationship shown in FIG. Here, it is possible to predict the depth at which the slag in the sand cover solidifies after the lapse of a desired period by setting a standard for determining “consolidated” when the predetermined uniaxial compressive strength is exceeded. Is possible.

  After the consolidation status is predicted by the above procedure, it is determined whether or not the predicted consolidation status is a desired status (S104). The determination of whether or not the situation is desired may be made by determining a standard according to the purpose of use and determining whether or not the condition is met. For example, when 10 cm of sand-covering material is placed for containment of seabed pollutants, it is required that a portion having a depth of 5 cm or more is consolidated when one year has passed since the sand-covering material was placed. And Whether the consolidation status after one year meets such a standard can be confirmed by confirming that the uniaxial compressive strength in the portion having a depth of 5 cm or more exceeds the strength according to the purpose of the sand covering. . If the standard is met, the temporarily determined steel slag is appropriate, and the sand covering work is actually performed using the sand covering material made of the steel slag (Yes in S105).

  If the predicted consolidated state is not the desired state (No in S105), the steel slag to be used is temporarily determined again (S102). The steel slag that is temporarily determined again is set to a slag different from the steel slag whose consolidated state has already been predicted. The steel slag that is temporarily determined again may be determined according to an empirical rule, or may be determined randomly. Factors to be changed in the temporary determination of the steel slag to be used include the type of steel slag, the particle size of the steel slag, and the like. For example, as shown in FIG. 4, when blast furnace granulated slag and steelmaking slag are mixed, if there is a tendency for the pH to rise more easily than blast furnace granulated slag alone, consolidation is achieved by adding steelmaking slag. It is possible to create a situation that is easy to do. When the slag to be used is changed, the reaction rate coefficient λ in Equation 3 is changed, and the pH distribution is changed.

  After the steel slag to be used is determined again, the consolidation status when the sand-covering material or backing material made of the temporarily determined steel slag is placed at the placement location, the hydroxyl ion concentration at the placement location Alternatively, prediction is made based on at least one of the calcium ion concentrations (S103), and it is determined whether or not the predicted consolidation state is a desired state (S104). When the predicted consolidated state matches the standard, the sand covering work is actually performed using the sand covering material made of steel slag (Yes in S105). If the predicted consolidation status does not meet the criteria, the steel slag is provisionally determined again and the consolidation status prediction is repeated until it is determined that the predicted consolidation status is the desired situation. .

  If the steel slag to be used as a sand-capping material or backing material is determined using the method for determining steel slag described above, an appropriate steel slag to be used can be determined according to the usage environment and purpose. Is possible. For example, when a sand-capping material is used for containment of seabed pollutants, it is possible to supply a sand-clad material that is suitable for containment of seabed pollutants and easily consolidated. In addition, when it is desired to expand marine resources on the sea floor, it is possible to effectively increase biological productivity by supplying sand-covering materials that are difficult to consolidate to the sea floor. Once materials such as sand-capping material and lining material are placed in the water area, it will be very difficult to reconstruct the work in terms of labor and cost even if it is discovered later that the material was not suitable. is there. Therefore, the method of the present invention, which can determine an appropriate steel slag in advance, is very beneficial with regard to the arrangement of sand covering material or backing material.

  2nd of this invention is related with the solidification condition prediction method of steel slag. This method is a method used in predicting the solidification state in the first aspect of the present invention. Specifically, the second aspect of the present invention is a method for predicting the solidification state of steel slag used as a sand-capping material or a backing material, where the sand-covering material or the backing material is disposed, and the steel slag used. , And on the basis of at least one of the hydroxyl ion concentration or the calcium ion concentration in the steel slag pore water in the arrangement location, the consolidated state when the sand covering material or the backing material made of the steel slag is arranged in the arrangement location This is a method for predicting the solidification status of steel slag. The second aspect of the present invention is used to predict the solidification state of steel slag, and is used to determine an appropriate steel slag to be used when the steel slag is used as a sand covering material or a backing material. The

  In the second implementation of the present invention, the description of the first of the present invention is applicable. Therefore, in the following description, the second outline of the present invention will be described.

  First, the arrangement | positioning location of a sand covering material or a backing material is determined. Moreover, the steel slag to be used is provisionally determined. Thereafter, the consolidated state when the sand-covering material or backing material composed of the steel slag is placed, the location of the sand-covering material or backing material, the steel slag used, and the hydroxyl ion concentration at the placement location Or predict based on the calcium ion concentration. At least one of the hydroxyl ion concentration or the calcium concentration is used.

  The prediction of the solidification state using these factors is as described in the first aspect of the present invention. For example, the consolidation state is predicted based on at least one of the time integral value of the hydroxyl ion concentration calculated based on the formula 1 or the time integral value of the calcium ion concentration calculated based on the formula 2. . The concentration of hydroxyl ions and the concentration of calcium ions can be calculated based on the advection / diffusion equation expressed by the above equation 3. In addition, the reaction rate coefficient λ in Equation 3 can be calculated by measuring the ion elution rate indicating the ion elution from the steel slag in the reference solution.

Example 1
FIG. 5 shows a schematic diagram of a method for predicting the consolidation state based on the time integral value of the hydroxyl ion concentration. Fresh water or seawater was placed in a constant temperature water tank that kept the water temperature constant (40 ° C. in this test), and a steel slag specimen was installed in the water. The specimen was filled with steel slag in a pipe such as polyvinyl chloride with the bottom closed, and the steel slag gap water and the water in the water tank were able to come and go from the top surface of the specimen. One of the specimens is provided with an opening (thin PVC pipe) for collecting slag pore water, and the other 7.5 cmφ specimen is not provided with an opening for the consolidation strength test. In this state, the specimen was cured underwater. The pH and calcium ion concentration of the pore water were determined by periodically collecting and measuring slag pore water.

  After a certain curing period, it was removed from the water and subjected to a strength test. The steel slag used here is blast furnace granulated slag (slag A) of the current particle size, short-time ground (slag B), and long-time ground (slag C). Shown in Moreover, the change with time of pH is shown in FIG. In addition, since pH was extract | collected from the center vicinity of a test body, 5 cm of upper and lower sides of the test body were cut off, and the center part of the test body was used for the compression test strength test.

  For the measurement of the consolidation strength, a hardness index by Yamanaka soil hardness tester (FIG. 8) was adopted. The reason is that using this measurement value, it is possible to determine whether or not the seabed is capable of inhabiting organisms, and the inhabiting environment for underwater organisms is 15 mm or less in the Yamanaka hardness index. This is because there are research results that are desirable. It has also been confirmed that the Yamanaka hardness index and the uniaxial compressive strength have the correlation shown in FIG.

FIG. 10 shows the relationship between the time-integrated value of the hydroxyl ion concentration obtained from the change with time of pH shown in FIG. 7 and the granulated slag consolidation strength (Yamanaka hardness index). From the results of curing tests in fresh water and seawater, the time of the hydroxyl ion concentration when the Yamanaka hardness index of the blast furnace granulated slag used in this test is 15 mm (the upper limit of the strength of the ground environment suitable for the habitat of aquatic organisms) The integral values can be determined as 3 × 10 ⁻³ [mol · day / L] and 3 × 10 ⁻² [mol · day / L], respectively.

  When the time required to reach the time integral value of the hydroxyl ion concentration shown above is calculated for each pH value of the steel slag pore water, the results shown in Table 1 are obtained.

  Thus, it can be seen that the lower the pH, the longer it takes to reach the desired consolidation strength. Here, what shows a result that requires a very long time, such as several tens of years, is considered not to be substantially consolidated.

  Using the above method, it is used to satisfy the required performance of sand covering according to the purpose of wanting to set or not to set from the prediction result of time and strength development after throwing steel slag into water. Steel slag to be selected can be selected.

Example 2
Next, an example of a test for obtaining the ion elution rate will be shown. In this test, first, according to the test of the Ministry of the Environment Notification No. 46 method, a container containing water and steel slag was continuously shaken, and the change in pH of the solution over time was measured. The steel slag used here is blast furnace granulated slag of the current particle size (slag A), ground for a short time (slag B), and ground for a long time (slag C). It was shown to. As shown in FIG. 11, although the pH suddenly listed in the initial stage, the rapid increase in pH ended 7 hours after “shaking”, and thereafter gradually approached a constant value. In this example, the ion elution rate (α) was calculated as the rate of increase until the pH value (hydroxyl ion concentration) at this time (after 7 hours) was reached. Α of slags A, B, and C were 6.5 × 10 ⁻⁶ , 2.1 × 10 ⁻⁴ , and 6.5 × 10 ⁻⁴ [mol / (L · day)], respectively.

  On the other hand, FIG. 12 shows a test apparatus simulating blast furnace granulated slag covering sand on the sea bottom, in which blast furnace granulated slag was introduced into a cylindrical container into which a pH meter was inserted from the side, and seawater was circulated. With this pH meter, the pH distribution in the depth direction within the ground granulated blast furnace slag can be measured. FIG. 13 shows the pH distribution in the sand cover. The pH in the ground granulated blast furnace slag is changed in the depth direction, and the rate of increase (slope) of pH with respect to the depth varies depending on the steel slag used (slag A <slag B <slag C). The reaction rate coefficient (λ) can be obtained using this rate of increase (slope) and Equation 3.

Specifically, Equation 3 can be transformed into Equation 6 below, where (λ / D) ^1/2 · log e is the rate of increase (slope), λ can be obtained, and slag A , B, and C were 0.03, 0.05, and 0.89 [1 / s], respectively.

  From the above two test results, when the relationship between the ion elution rate (α) and the reaction rate coefficient (λ) was obtained, the result shown in FIG. 14 was obtained, and the correlation could be confirmed. By substituting the reaction rate coefficient (λ) determined from the ion elution rate (α) into λ of Equation 3, the ion concentration distribution in the sand cover or backfill can be obtained by the advection diffusion equation. Furthermore, by using the relationship between the pH and calcium ion concentration and the expression of the consolidation strength shown in the previous embodiment, it is possible to predict the consolidation state in the sand cover or backfill.

  By obtaining the ion elution rate in this way, the reaction rate coefficient (λ) in Equation 3 can be determined, and in order to obtain the desired consolidation strength, that is, pH and calcium concentration conditions for sand-capping or backfilling. The steel slag suitable for the case can be determined.

Ca ^{2+, SiO 4-,} and Al _{(OH) 4} ^- and each ion is a graph showing the relationship between the pH. In FIG. 1A, the vertical axis represents the concentration of Ca ²⁺ , in FIG. 1B, the vertical axis represents the concentration of SiO ⁴⁻ , and in FIG. 1C, the vertical axis represents the concentration of Al (OH) ₄ ⁻ . It is a graph which shows the relationship between the density | concentration of a hydroxyl ion, and consolidation strength. The horizontal axis is the cumulative integrated value of hydroxyl ions, and the vertical axis is the uniaxial compressive strength of steel slag. It is a flowchart explaining the determination method of the steel slag of this invention. The pH distribution in the sand cover when only blast furnace granulated slag is arranged as sand covering material, and the pH distribution in the sand cover when a mixture of blast furnace granulated slag and steelmaking slag is arranged as sand covering material are shown. It is a graph. Schematic of the method of predicting a consolidation condition by the time integral value of hydroxyl ion concentration. It is a figure which shows the particle size distribution of blast furnace granulated slag A, B, C used for the test. It is a figure which shows the time-dependent change of the pH of pore water. It is a photograph of a Yamanaka type soil hardness meter. It is a figure which shows the relationship between a Yamanaka type | formula soil hardness index | exponent and uniaxial compressive strength. It is a figure which shows the relationship between the time integral value of a hydroxyl group ion, and a Yamanaka formula hardness. It is a figure which shows pH change with time of the solution in a shaking test. It is the test equipment figure which poured blast furnace granulated slag into the cylindrical container which inserted the pH meter from the side, circulated seawater, and imitated blast furnace granulated slag covering sand of the seabed. It is a figure which shows the pH distribution result in granulated slag covering sand. It is a figure which shows the relationship between ion elution rate ((alpha)) and reaction rate coefficient ((lambda)).

Claims (9)

A method for determining steel slag used as sand-capping material or backing material,
A step (a) of determining the location of the sand-capping material or the backing material;
A step (b) of tentatively determining the steel slag used;
The caking condition when the sand-covering material or backing material made of steel slag that has been provisionally determined is placed at the placement location is set to at least one of the hydroxyl ion concentration or the calcium ion concentration in the steel slag pore water at the placement location. Predicting based on (c);
Determining whether the predicted consolidated situation is a desired situation (d);
A method for determining steel slag, comprising:   Steps (b), (c), and (d) were predicted for a steel slag that is different from the already determined steel slag when the predicted consolidated state is determined not to be the desired one. The method for determining steel slag according to claim 1, wherein the method is repeated until it is determined that the consolidation state is a desired state. The step (c) is based on at least one of a time integral value of the hydroxyl ion concentration calculated based on the following formula 1 or a time integral value of the calcium ion concentration calculated based on the following formula 2. The method for determining steel slag according to claim 1, wherein the method is a step of predicting the situation.
(In the formula, [OH ⁻ ] represents the hydroxyl group ion concentration in the pore water at the arrangement location, and t represents time)
(In the formula, [Ca ²⁺ ] represents the calcium ion concentration in the pore water at the arrangement location, and t represents time) 4. The steel according to claim 3, wherein the concentration of hydroxyl ions in Formula 1 and the concentration of calcium ions in Formula 2 are calculated based on an advection / diffusion equation expressed by Formula 3 below. How to determine slag.
(In the formula, C is the concentration of hydroxyl ion or calcium ion (mol / L), t is time (s), D is a diffusion coefficient, and h is from the upper surface of the sand-capping material or backing material. Is the reaction rate coefficient (1 / s) indicating the ease of elution of hydroxyl ions or calcium ions from the slag, and ν is the pore water velocity (cm / s). is there)   5. The reaction rate coefficient λ is calculated by measuring an ion elution rate α (mol / L · s) indicating ion elution from a steel slag in a reference solution. The method for determining steel slag as described. A method for predicting the solidification status of steel slag used as sand-capping material or backing material,
Based on at least one of hydroxyl ion concentration or calcium ion concentration in the location where the sand covering material or the backing material is disposed, the steel slag used, and the steel slag pore water in the location, or the sand covering material comprising the steel slag A method for predicting the solidification status of steel slag, wherein the consolidation status when a backing material is arranged at the arrangement location is predicted. The consolidation state is predicted based on at least one of the time integral value of the hydroxyl ion concentration calculated based on the following equation 1 or the time integral value of calcium ion concentration calculated based on the following equation 2. The method for predicting solidification status of steel slag according to claim 6, wherein the method is characterized.
(In the formula, [OH ⁻ ] represents the hydroxyl group ion concentration in the pore water at the arrangement location, and t represents time)
(In the formula, [Ca ²⁺ ] represents the calcium ion concentration in the pore water at the arrangement location, and t represents time) 8. The steel according to claim 7, wherein the concentration of hydroxyl ions in Formula 1 and the concentration of calcium ions in Formula 2 are calculated based on an advection / diffusion equation represented by Formula 3 below. A method for predicting slag solidification.
(In the formula, C is the concentration of hydroxyl ion or calcium ion (mol / L), t is time (s), D is a diffusion coefficient, and h is from the upper surface of the sand-capping material or backing material. Is the reaction rate coefficient (1 / s) indicating the ease of elution of hydroxyl ions or calcium ions from the slag, and ν is the pore water velocity (cm / s). is there) The reaction rate coefficient λ is calculated by measuring an ion elution rate α (mol / L · s) indicating ion elution from a steel slag in a reference solution. The solidification state prediction method of the described steel slag.